1. Field of the Invention
Modern internal combustion engine design is undergoing important changes to meet stricter standards concerning engine and exhaust gas emissions. One major change in engine design is the feeding of blow-by gases from the crankcase zone of the engine into the intake air-fuel mixture at the carburetor just below the throttle plate, rather than venting these gases to the atmosphere as in the past. The blow-by gases contain substantial amounts of deposit forming substances and are known to form deposits in and around the throttle plate area of the carburetor. Another significant change is the recirculation of a part of the exhaust gases to the fuel air intake of the engine. These exhaust gases also have deposit forming tendencies. The deposits caused by the recirculated gases both blow-by and exhaust gases restrict the flow of air through the carburetor at idle and at low speeds so that an overrich fuel mixture results. This condition produces rough engine idling and stalling and leads to the release of excessive hydrocarbon exhaust emissions to the atmosphere.
Certain gamma and delta acid lactones or mixtures thereof have been described as corrosion inhibitors for hydrocarbon oils boiling from about 75.degree. to 900.degree. F. These materials were obtained by reacting an alkenyl-substituted succinic acid, such as tetrapropenyl succinic acid, with a dilute mineral acid at a temperature ranging from about 100.degree. to 212.degree. F. to effect internal esterification of the alkenylsuccinic acid to form the acid lactone reaction product. While the structure of individual acid lactones has been postulated, because of the variety of positions of the olefinic bond in the alkenyl radical and the further fact that internal esterification of alkenyl succinic acid takes different paths leading to five and six-membered ring structures, the product obtained from the foregoing reaction are complex mixtures of five- and six-membered hydrocarbon substituted lactones, each five- and six-membered type exhibiting a variety of structural configurations.
2. Description of the Prior Art
U.S. Pat. No. 3,248,187 discloses a hydrocarbon oil composition, such as gasoline, which has been inhibited against rust by the addition thereto of acid lactone reaction product. Gamma and delta lactones derived from an alkenyl-substituted succinic acid are specifically disclosed.
U.S. Pat. No. 3,997,569 discloses a method for preparing certain substituted acid lactones reaction products which are useful in a motor fuel composition.